The Center for Disease Control and Food and Drug Administration are investigating a string of E. coli infections across the U.S. The organizations say the bacteria is "closely related genetically" to the Canadian strain that's been reported 41 times in five provinces.

“There is not enough epidemiologic evidence at this time to indicate a specific source of the illnesses in the United States,” CDC spokesperson Brittany Behm told Consumer Reports on Wednesday. “Although some sick people reported eating romaine lettuce, preliminary data available at this time shows they were not more likely than healthy people to have eaten romaine, based on a CDC food consumption survey.”

Since the cause of the outbreak hasn't been pinpointed in the U.S., an official recall hasn't been released by the FDA or CDC. But it's still a good idea to avoid the leafy green for now, whether it's sold fresh or in pre-packaged salad mixes.

Unfortunately, washing the vegetable won't remove all traces of the bacteria.

"If you've got bacteria on the surface of fruits and vegetables, and you give them a wash with cold water, it removes some of what's on the surface," explained Brendan Niemira of the USDA's Microbial Food Safety Unit in Pennsylvania. "...It [cold water rinsing] doesn't remove all of them, and that's a problem. If things are well-attached or living in a tight-knit community called a biofilm, that's going to be hard to get rid of."

According to the Mayo Clinic, symptoms of e. Coli usually begin three to four days after exposure. They may include nausea, vomiting, abdominal cramps, pain or tenderness and diarrhea.